Some U.S. Senators are demanding answers after an Air Force commander dismissed a sexual assault conviction against one of his officers. Lieutenant Colonel James Wilkerson had been sentenced to a year in prison and dismissal from the military for aggravated sexual assault, but he's been reinstated. Senators Jean Shaheen and Barbara Boxer called the decision a travesty of justice. They and Senator Claire McCaskill have written to defense officials about the case.

For details, we're joined by reporter Nancy Montgomery. She's been following the case for Stars and Stripes, which covers the military. And Nancy, to start, give us some background. What are the basic facts of this case?

NANCY MONTGOMERY: Back in November there was a court marshal at Aviano Air Base. And the defendant was Lieutenant Colonel James Wilkerson. He's a fighter pilot and he happened to be the base inspector general for maintenance. And he was accused of assaulting a sleeping house guest after an impromptu party at his house. She was a 49-year-old physician's assistant, a civilian. And after a week-long trial, a jury of four colonels and a lieutenant colonel found him guilty. And they sentenced him, as you said, to dismissal, a year in jail and forfeiture of all paying allowances.

CORNISH: So tell us a little bit more about that court marshal. What was unusual about what took place that week?

MONTGOMERY: Well, it was unusual that it involved such a high-ranking officer. And it was unusual in that it went for a week. It was a pretty long court marshal, as these things go. And I think, you know, at the time it was hailed by women's advocates as, you know, an example of the Air Force taking sexual assault seriously. Because here you had a very powerful person with powerful friends in the chain of command who, nonetheless, had been brought up on charges and convicted.

CORNISH: Now, the commander of the third Air Force, Lieutenant General Craig Franklin, has overturned that court's decision. Explain to us how he was able to do that and the reason he may have given for doing it.

MONTGOMERY: The UCMJ, the Uniform Code of Military Justice, and the rules for courts marshal specifically give unfettered authority to the convening authority, the person who brings the court marshal, which was Franklin. They give them authority to do whatever they want to at the end of the case. If they want to, you know, reduce the sentence, throw out a charge, that's fine. They can't increase any penalty or punishment but they can reduce it, they can give clemency. And that's what he did.

And - only he dismissed the entire case, which is exceedingly rare, everyone says. He said, in his view, the burden on the prosecution to prove beyond a reasonable doubt the guilt of the defendant had not been met.

CORNISH: You mentioned that people had been watching this case. And is it seen as some kind of measure of the military's ability to prosecute allegations of sexual assault or rape? I mean, the fact that the court marshal, you know, it takes place within the chain of command and I'm wondering if this overturning of it has made a big difference.

MONTGOMERY: Well, I think previously the criticisms of how the military handles sexual assaults and the bias that has been alleged to be in the system has sort of focused on the lower level commanders, that they did not move forward with these cases, that they did not send them to court marshal or have them investigated. And so, last year, Secretary of Defense Leon Panetta kicked the authority to do that up the chain of command to the colonel level, the 06 level.

This time everything worked, as somebody told me. You know, the guy was prosecuted, it went to court marshal, it was a successful prosecution. And then, at the other end of the chain of command, the very top, it was overturned.

CORNISH: And so what's been the reaction from the Pentagon? You know, you have these senators asking questions. Is there any sense that the military's going to rethink or review the way it handles these kind of cases?

MONTGOMERY: Well, they haven't really said a lot publicly. I think that, you know, if you have three senators calling for investigations and wanting answers, that they're probably going to have to deal with it somehow. I mean, the idea that the decisions about how sexual assaults are handled should not be with the chain of command, that's not new. But I've been told by, you know, legislators that they think that this will give added impetus to that, and that this case could be, as they call it, a tipping point.

CORNISH: Well, Nancy, thank you so much for explaining the case to us.

MONTGOMERY: Thank you.

CORNISH: Nancy Montgomery is a reporter for Stars and Stripes. We were talking about the case of Air Force Lieutenant Colonel James Wilkerson, who was tried and convicted on sexual assault charges. The commander of the 3rd Air Force has set aside that conviction and reinstated Wilkerson. Transcript provided by NPR, Copyright NPR.